1. Field of the Invention
The present invention relates to a hydraulic pressure supply system of an automatic transmission. More particularly, the present invention relates to a hydraulic pressure supply system of an automatic transmission for a vehicle which changes its mode from full discharge mode to two circuit mode or half discharge mode according to variable control pressure of a solenoid valve.
2. Description of Related Art
A gear pump is mainly used as a hydraulic pump applied to a hydraulic pressure supply system of an automatic transmission for a vehicle. However, a vane pump that can supply sufficient oil at a low speed region is recently used.
The vane pump increases discharge amount in proportion to a rotation speed thereof. If the vane pump is controlled to supply the sufficient oil at the low speed region, unnecessarily much oil is supplied and thereby causes driving loss of the pump at a high speed region.
Therefore, the vane pump includes first and second pump chambers disposed on a shaft of a rotor so as to recirculate surplus oil at the high speed region.
The first pump chamber is a main pump chamber, and hydraulic pressure generated at the first pump chamber is supplied to a high pressure portion (friction members, pulleys and so on).
In addition, the second pump chamber is a sub pump chamber, and hydraulic pressure generated at the second pump chamber is supplied selectively to the high pressure portion (friction members, pulleys and so on) or a low pressure portion (torque converter, cooling device, lubrication device and so on), or is recirculated.
In further detail, the hydraulic pressure generated at the first pump chamber and the second pump chamber is supplied to the high pressure portion if an engine speed is low, but the hydraulic pressure generated at the second pump chamber is recirculated to an inlet side if the engine speed is high. Therefore, driving loss of the pump may be minimized and fuel economy may be enhanced.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.